The present invention relates to the recordal of digital data on a digital video recorder, and more particularly to the use of a digital video recorder as a universal data recorder.
Digital video tape recorders are well known. Due to their high cost, such devices are currently used primarily by television programmers and broadcasters to record television programs in a high quality digital format. The programs may then be transmitted in a conventional format such as over the airwaves, via satellite, or via a cable television network for receipt by television viewers. It is expected that the cost of digital video tape recorders will substantially decrease in the future. At such time, such apparatus is expected to become a consumer product, replacing current analog video tape recorders used in the home.
Digital video tape recorders receive signals in a conventional digital television format. For example, a digital format analogous to the standard NTSC (National Television Systems Committee) format used to broadcast television signals in North America can be used. The NTSC format provides television channels in six MHz bandwidths that carry video information on a line-by-line basis. The video information for a given television line is preceded by timing and control information for the video data on that line.
Various systems are known for transmitting data on an analog video waveform. For example, scrambled digital audio information can be transmitted in nonvideo portions of a video waveform. Two such systems are disclosed in U.S. Pat. No. 4,563,702 entitled "Video Signal Scrambling and Descrambling Systems" to Heller, et al and U.S. Pat. No. 4,613,901 entitled "Signal Encryption and Distribution System for Controlling Scrambling and Selective Remote Descrambling of Television Signals" to Gilhousen, et al. These systems provide for digital stereo audio transmission in the horizontal blanking interval of an NTSC television signal.
In another known system, described in U.S. Pat. No. 4,787,085 entitled "Digital Signal Transmitting System" to Suto, et al, digital signals that are not limited to audio and video components of a television signal are time division multiplexed and modulated to form a signal having a bandwidth corresponding to one channel portion of a television broadcast signal. A receiver extracts the digital data corresponding to a desired signal and supplies it to an appropriate appliance such as a computer, stereo set, or facsimile machine that converts the data into a useful form for a user. In the Suto, et al system, all signals are transmitted in a digital format, requiring a separate receiver that is not compatible with existing cable television converters or satellite television receivers.
Improvements in television signal transmission and reception are currently being developed using digital techniques. For example, high definition television systems are expected to be commercialized in several years that transmit compressed digital audio and video information to provide television quality far superior than that currently available. Encoders for processing the digital HDTV signals are very expensive. It would therefore be advantageous to provide a system for sharing a single encoder among various television programs. One way to do this would be to record separately encoded program signals for subsequent transmission via satellite, cable or over the air. In this manner, a single encoder could be used to encode any number of programs for recordal prior to transmission. These prerecorded programs could then be transmitted at any time according to a broadcaster's programming schedule.
It would be further advantageous to provide a relatively simple and inexpensive scheme for recording random data on a digital video recorder. The term "random data" as used herein means data that is not limited to television signal (i.e., audio and video) data. In the HDTV context, such data can include the compressed video digital data stream as well as audio data, access control data, and timing data for a television signal. Such data could also comprise nontelevision data, such as any digital data stream received from a computer or other device. The ability to use a digital video recorder to record such random data would obviate the need to purchase a separate storage device to store nonvideo data.
The present invention provides an interface that enables the recording and playback of random data on a digital video recorder. The interface connects to the input and output ports of a standard digital video recorder, without requiring modification of the recorder circuitry.